Anticancer polyheterocyclic compounds and associated methods

This application claims the benefit of U.S. Provisional Patent Application No. 63/661,432, filed Jun. 18, 2024, entitled “Anticancer Polyheterocyclic Compounds and Associated Methods,” the entirety of which is hereby incorporated by reference.

This invention was made with government support under CHE-2247411 awarded by National Science Foundation. The government has certain rights in the invention.

The present invention relates to complex molecules and synthesis thereof. In particular, but not by way of limitation, the present invention relates to polyheterocyclic compounds and synthesis thereof.

Quinone-based organic molecules play important roles in developing therapeutic drugs, agrochemicals, and functional materials and acting as building blocks in total synthesis. Notably, in benzoquinone derivatives incorporated with heteroatoms such as nitrogen or oxygen, the redox potential of the innate carbonyl groups increases, thus significantly enhancing the biological activities of the resulting heterocycles.

Abundant and easily accessible, aromatic compounds with stabilized cyclic n-electron systems, such as benzene, naphthalene, pyridine, and quinoline, serve as natural feedstocks. Commonly utilized in organic synthesis are the well-established synthetic transformations that involve introducing and manipulating functional groups on aromatic rings, making a diverse range of substituted aromatics prevalent as starting materials. This context has spurred considerable interest in dearomatization reactions, aiming to swiftly construct complex, non-planar scaffolds from planar aromatic compounds.

A primary challenge in achieving such transformations lies in overcoming the inherent stabilization of aromatic systems. Notably, recent advancements have introduced sustainable approaches to dearomatization, leveraging visible light-induced photochemical methods. These methods, involving energy or electron transfer, have been successfully applied to numerous aromatic feedstocks, including arenes, phenols, indoles, heteroarenes, and more.

Despite recent strides in the development of dearomatization strategies for synthesizing valuable organic molecules, the task of selectively converting benzene rings into the corresponding saturated or partially saturated cyclic carbon skeletons under mild reaction conditions remains exceptionally challenging.

Thus, there is a need for an improved method of synthesizing such complex molecules as well as for the resulting complex molecules with unique structures enabled by such improved synthesis methods.

The following presents a simplified summary relating to one or more aspects and/or embodiments disclosed herein. As such, the following summary should not be considered an extensive overview relating to all contemplated aspects and/or embodiments, nor should the following summary be regarded to identify key or critical elements relating to all contemplated aspects and/or embodiments or to delineate the scope associated with any particular aspect and/or embodiment. Accordingly, the following summary has the sole purpose to present certain concepts relating to one or more aspects and/or embodiments relating to the mechanisms disclosed herein in a simplified form to precede the detailed description presented below.

In an embodiment, a method of building complex molecules based on a complexity building photoinduced cascade approach is described.

In a further embodiment, complex molecules with highly complex molecular structures enabled by the complexity building photoinduced cascade approach are described.

These and other features, and characteristics of the present technology, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. As used in the specification and in the claims, the singular form of ‘a’, ‘an’, and ‘the’ include plural referents unless the context clearly dictates otherwise.

For simplicity and clarity of illustration, the drawing figures illustrate the general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the embodiments detailed herein. Additionally, elements in the drawing figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of the described embodiments. The same reference numerals in different figures denote the same elements.

The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. In the following detailed description, references are made to the accompanying drawings that form a part hereof, and in which are shown by way of illustrations or specific examples. These aspects may be combined, other aspects may be utilized, and structural changes may be made without departing from the present disclosure. Example aspects may be practiced as methods, systems, or apparatuses. The following detailed description is therefore not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims and their equivalents.

The invention includes a synthesis approach based on complexity building photoinduced cascade and complex molecules synthesized using this approach. Existing methods do not allow for synthesis of such complex molecules with the reduced number of synthesis steps enabled by the presently described approach. By taking advantage of a modular design of photo-precursors, the present approach allows a photoinduced multi-step cascade approach, leading to considerable growth of molecular complexity in very few, experimentally simple steps.

It is understood by a person of ordinary skill in the art that substitutions on the benzene ring of the benzoquinoline moiety are within the scope of the invention. Such replacement of one or more of the hydrogen atoms with deuterium, halogen, C-Calkanes, ethers, amides, esters, polyols, polyethers, and polyamines, each independently selected, is contemplated. This is a non-limiting list of replacement substituents. Such simple substitutions are also contemplated in other moieties within the compounds.

SCHEME 1 illustrates experimentally simple modular access to photoprecursors 4 by linking arylamine (or heteroarylamine) (1) and 2-amino-naphthoquinone (3) with oxalyl amide tether, in accordance with an embodiment. Alternatively, amide formation between aminonaphthoquinone and an aromatic group carrying an appropriately tethered carboxylic acid may be used as the linking mechanism, such as a substituted arylpropanoic acid (or heteroarylpropanoic acid such as furanpropanoic acid). Irradiation of photoprecursors 4 in a solvent such as dimethyl sulfoxide (DMSO) with an ultraviolet (UV) light source, such as light emitting diode (LED) array emitting light in a lamba max (λ) of 410-420 nm wavelength, a mercury UV lamp, solar radiation, among others, triggers their conversion to hydroquinone 5 in a single experimental step photoreaction. Subsequent oxidation of hydroquinone 5 leads to the formation of quinone 6, effectively preventing the cycloreverting of the molecules to their photoprecursors.

The photoreaction mechanism disclosed herein is a [3+2]cycloaddition initiated by Excited State Proton Transfer (ESIPT). During this reaction, a reactive 1,3-diradical is produced. This is in contrast with our earlier work that used a [4+2]cycloaddition via ESIPT-generated 1,4-diradicals.

This photoinduced cascade approach has a broad scope as illustrated by TABLE 1, showing a number of photocascade products with isolated yields, in accordance with certain embodiments. Reaction conditions may be optimized by nuclear magnetic resonance (NMR) scale experiments with acetone, DMSO, methanol, acetonitrile, dichloromethane (DCM), and toluene, for example. In embodiments, DMSO may be particularly suitable as a solvent.

In embodiments, the reactions involved in the synthesis process may be at ambient temperature without explicit temperature control. The structures and stereochemistry of the photoproducts with the aid of DU8ML, a machine learning-augmented density functional theory (DFT) computational method, to perform calculations of the NMR spectra.

For example, in the primary [3+2] photoaddition, the photoprecursor 4d of TABLE 1 displays two possibilities. The major product may subsequently be formed with the active involvement of a methoxy-substituted n-system. A parallel outcome was noted with photoprecursor 4f of TABLE 1, where the minor product was not observable.

Another potentially important feature demonstrated by the photoproducts 6i and 6j is that, due to the ease of outfitting di-allyl or di-propargyl with additional unsaturated functionalities, these products may serve as synthons for subsequent post-photochemical modifications. For instance, ring-closing metathesis and click reactions may be implemented for synthesis of molecules with further complexity.

This approach may be adapted for polyheterocyclic scaffolds, some examples shown in TABLE 2. Similar to the complex quinone formation summarized in TABLE 1, this pathway may be utilized as a primary photoreaction leading to various quinones embedded in polyheterocyclic scaffolds, even with precursors lacking a reactive alkenyl. These scaffolds, in turn, may serve as synthons in subsequent complexity-building transformations, in certain embodiments.

As an example, photoprecursors 4 were synthesized, equipped with unreactive benzyl, or relatively less reactive 2-furyl-methyl. The N-benzyl photoprecursor 4m yielded a [3+2]cycloaddition product, featuring a reactive diene for further complexity-building transformations. In an embodiment, photoprecursor 4n exhibits solvent-dependent cycloaddition. Irradiation in DMSO may result in the [3+2] photoproduct 6n. Conversely, irradiation in DCM produced [3+4] photoproduct 7m, where the furan n-system was involved in the addition.

Similarly, solvent-dependent cycloaddition may be observed in the case of photoprecursor 4n. For instance, replacing the phenyl n-system with the 3-thiophene n-system results in a heterocyclic fused photoproduct 6p via simple [3+2] addition.

As discussed above, photoprecursor 4 retained its photo-active core after the oxidation of the primary photoproduct 5. Further irradiation of photoproduct 6 may result in further post-photochemical transformation, as illustrated in SCHEME 2. In an embodiment, photoproduct 4a, upon additional irradiation, resulted in a rearranged cyclobutane-fused photoproduct 8a. The homolytic cleavage of the (N)C—C(OMe) bond produces a biradical transition state, which may resonate into its allylic version, in certain embodiments. The recombination of biradicals may lead to the formation of the rearranged product 8a. This photo-rearrangement transformation also may extend to the primary photoproduct 6c, resulting in a rearranged product 8c.

Further, in embodiments, the thermal reaction of photoproduct 6a in DMSO results in the formation of the benzo[f]indole fused product 9a. A mechanistic pathway for this transformation is illustrated in SCHEME 3, in an embodiment. Initially, the demethylation of photoproduct 6a led to an intermediate C This intermediate participated in a Grob-like fragmentation, giving rise to the benzo[f]indole fused azabicyclodecenone D. Subsequently, hydrolysis of the imidazolidinedione moiety, followed by decarboxylation, produces a N-formyl intermediate F. This intermediate may further participate in a Pummerer rearrangement, ultimately yielding the product 9a in certain embodiments.

Referring to SCHEME 4, subjected to straightforward yet advantageous post-photochemical transformations, the primary photoproducts may enhance the complexity and diversity of the core scaffold or adorn the cores with various functionalities and (hetero)aromatic pendants. For example, a primary photoproduct 6m contains a reactive cyclohexadiene fragment that can readily participate in [4+2]cycloaddition reactions, including hetero-Diels-Alder reactions with 1,2,4-triazole (a) of SCHEME 4). Subsequently, the dihydrofuran photoproducts (6o and 6h) readily reacted with oxabutadiene, generated in situ from 1,3-dicarbonyl compound, resulted more complexe oxa-Diels-Alder compounds 11o and 11h respectively (5b of Scheme 4).

5c of SCHEME 4 depicts the reaction of 6 h with a 1,3-dipole, bromonitrile oxide, generated in situ from dibromoformaldoxime, leading to the formation of a complex polyheterocycle 12h, in certain embodiments. Given its numerous reactive functionalities, this compound can be believed a valuable synthon for further scaffold diversification.

The processes described above may be used for the synthesis of complex molecules particularly suitable for cancer treatment. For example, results of National Cancer Institute (NCI) 5-dose testing of compounds are shown in Table 4.

As generally understood among experts of anticancer research, the one-dose mean graph shows the percent growth of treated cells, in a manner similar to mean graphs from a 5-dose assay (see https://dtp.cancer.gov/discovery_development/nci-60/methodology.htm). The number reported for the one-dose assay is growth relative to a no-drug control, and relative to the time zero number of cells. This approach allows detection of both growth inhibition (values between 0 and 100) and lethality (values less than 0), which is the same approach as the visualization of results for a 5-dose assay. For example, a value of 100 means no growth inhibition. A value of 40 would mean 60% growth inhibition. A value of 0 means no net growth over the course of the experiment. A value of −40 would mean 40% lethality. A value of −100 means all cells are dead.

As used herein, the recitation of “at least one of A, B and C” is intended to mean “either A, B, C or any combination of A, B and C.” The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The terms and expressions employed herein are used as terms and expressions of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof. Each of the various elements disclosed herein may be achieved in a variety of manners. This disclosure should be understood to encompass each such variation, be it a variation of an embodiment of any apparatus embodiment, a method or process embodiment, or even merely a variation of any element of these. Particularly, it should be understood that the words for each element may be expressed by equivalent apparatus terms or method terms-even if only the function or result is the same. Such equivalent, broader, or even more generic terms should be considered to be encompassed in the description of each element or action. Such terms can be substituted where desired to make explicit the implicitly broad coverage to which this invention is entitled.

As but one example, it should be understood that all action may be expressed as a means for taking that action or as an element which causes that action. Similarly, each physical element disclosed should be understood to encompass a disclosure of the action which that physical element facilitates. Regarding this last aspect, by way of example only, the disclosure of a “protrusion” should be understood to encompass disclosure of the act of “protruding”-whether explicitly discussed or not-and, conversely, were there only disclosure of the act of “protruding”, such a disclosure should be understood to encompass disclosure of a “protrusion”. Such changes and alternative terms are to be understood to be explicitly included in the description.

Experimental procedures for compounds synthesized are shown below:

Common solvents were purchased from Fisher Scientific and used as is. Common reagents, aldehydes, and alkyl halides were purchased from Sigma-Aldrich, TCI America, AK Scientific, Oakwood Chemical or AstaTech and used without additional purification. NMR spectra were recorded at 25° C. on a Bruker Avance III 500 MHz instrument in CDCl(unless noted otherwise) using residual solvent peaks as an internal standard (δ7.26 ppm, δ77.16 ppm for CDCl; δ2.50 ppm, δ39.52 ppm for DMSO-d). The description of signals includes s=singlet, d=doublet, dd=doublet of doublets, t=triplet, dt=doublet of triplets, td=triplet of doublets, q=quartet, m=multiplet, br.s=broad singlet. The structural assignments were made with additional information from gCOSY, gHSQC, and gHMBC experiments. X-ray structures were obtained with a Bruker APEX II instrument. High-resolution mass spectra were obtained on a Waters Synapt G2 HDMS Quadrupole/ToF mass spectrometer with electrospray ionization (Central Analytical Laboratory, University of Colorado Boulder). Flash column chromatography was performed using Teledyne Ultra-Pure Silica Gel (230-400 mesh) on a Teledyne Isco Combiflash Rf. The light-promoted reactions were carried out using An irradiator containing two visible light LEDs (High Power LED Star #A008-UV410-48; λ=410-420 nm; board configuration: 3-Up A008) installed on a heat sink with fan and driven by a RACD 30-700 power supply (output: 700 mA, 10-43 VDC), was placed ca. 2-5 mm away from the irradiation window. Borosilicate glass reaction vessels were typically distanced from a light source in a 5-7 cm range.

Prepared according to a modified literature protocol.1,4-Naphthoquinone (6.39 mmol) was suspended in THF-water 4:1 (20 mL). Solution of sodium azide (19.2 mmol) in water-AcOH 3:1 (4 mL) was added, and the mixture was stirred at ambient temperature for 12 h. After the removal of volatiles by evaporation, water (30 mL) was added, and then the product was extracted with DCM (4×150 mL). The combined organic layers were washed with sat. aq. NaHCO(30 mL), dried over anhydrous NaSO, filtered, and the solvent was removed under reduced pressure to afford a title compound (3).H NMR (500 MHz, CDCl) δ 8.07 (ddd, J=10.8, 7.7, 0.9 Hz, 2H), 7.73 (td, J=7.6, 1.3 Hz, 1H), 7.64 (td, J=7.6, 1.3 Hz, 1H), 6.00 (s, 1H), 5.13 (br s, 2H).

To a stirred solution of Boc-protected aniline (1.0 mmol) in DMF (10 mL) were sequentially added NaH (60 mg, 1.5 mmol, 60% in mineral oil) and alkyl bromide/chloride (1.25 mmol) at 0° C. The resulting solution was stirred at ambient temperature for 15 h. After the completion of the reaction (the progress of the reaction was monitored byH NMR), water (20 mL) was added at 0° C., and organics were extracted with ethyl acetate (3×30 mL). The combined organic extracts were washed with water (2×50 mL), and dried over anhydrous NaSO, then concentrated under reduced pressure to give a crude yellow oil. The crude product was dissolved in DCM and TFA (10 mL, 5:1 v/v ratio), and stirred at ambient temperature for 3 h. The progress of the reaction was monitored byH NMR. After completion of the reaction, the volatiles were removed under vacuum, and a saturated solution of NaHCO(10 mL) was added. Organics were extracted with DCM (3×30 mL), and the combined organic extracts were dried over anhydrous NaSO, and the solvent was removed under reduced pressure to afford secondary anilines. The crude compound was purified by flash chromatography on silica gel to give the desired products.